1. Field of the Invention
The present invention relates to a vehicle air conditioner which detects a humidity in a passenger compartment and prevents a windshield from being fogged.
2. Description of Related Art
In a conventional vehicle air conditioner described in JP-A-7-179120, an air humidity inside a passenger compartment is detected by a humidity sensor, and defogging operation of a windshield of the vehicle is performed. Specifically, when the windshield of the vehicle satisfies a fogging condition, operation of the compressor is controlled so that a temperature of air after passing through an evaporator disposed in an air conditioning duct becomes a predetermined temperature that is calculated based on the detected humidity of the humidity sensor to defog the windshield.
In this vehicle air conditioner, the humidity sensor is disposed in an air passage through which air flows into the passenger compartment, to detect the humidity of air passing through the air passage. Further, an aspirator is disposed in the air passage, so that a negative pressure is generated in accordance with an air flowing amount in the air passage. Therefore, an air amount corresponding to the air flowing amount in the air passage is ventilated in the passenger compartment.
When a water temperature flowing into a heater core is low at a time immediately after an engine start in a low outside air temperature, a blower for blowing air into the passenger compartment through the air passage is stopped or is operated by a low blowing level (low air amount). However, in this case, air (inside air) in the passenger compartment is not ventilated or is slightly ventilated, and the humidity inside the passenger compartment may be increased. Further, the humidity sensor detects the humidity of air after passing through the evaporator. Therefore, the predetermined temperature for defogging the windshield is calculated based on the detected humidity that is lower than an actual humidity of the passenger compartment. Accordingly, in this case, the windshield may be readily fogged.